Specification: Frequency: 900, 1800,(Pls do not plug the CDMA sim card for the device,It will not work with the CDMA Card) Embed four condense microphone 24 hours continuous usage. All GSM SIM card compatible Microphone range: 10~14 Meters (diameter), 4 direction Receive sensitivity: -\+ 10K Working temp: -40~50 degree C Responding frequency: 1.2K~800Khz Stand-by time: 4 --7days Dimension:  6*4*1.2 cm